Gen 1:1 "In the beginning, God created the Heavens and the Earth"
Gen 1:2 "The earth was without form and void..."
God does not create things "without form and void". The original Hebrew words used there imply an indistinguishable ruin and darkness.
Scientists believe the Universe to be billions of years old. It is possible that God created the Heavens and the Earth that long ago, and that He was doing something with it, when Satan rebelled and was cast down. Down - that is, into the physical universe God had created. Thus was can suggest that Satan was the cause of the indistinguishable ruin and darkness.
Following this line of reasoning... The "Creation" as traditionally told would still have happened about six thousand years ago, but with this undefined period of time before it during which Satan was cast down.
This would also give another good reason for the Creation of man in God's image: Satan had destroyed the universe, and god had just finished fixing it. So He created representative figures in His image with power and authority in the physical universe. It's all connected to God's plan to destroy Satan for good, and bring many children in to Himself.
To address the question of WHEN the angels were created... Given what was said above, it would have to be some time between Gen1:1 and Gen1:2.